The mother of a dead 1-year-old Missouri boy told police she struck him repeatedly when he wouldn't stop crying or lie down, then left his body near a nearby graveyard, St. Louis County, Mo., prosecutor Bob McCulloch said at a news conference this afternoon.

Shelby Dasher, 20, is being charged with second-degree murder, and is being held on a $500,000 cash bond, McCulloch said. She is on suicide watch, he said.

The medical examiner reported the cause of death of Dasher's son, Tyler Dasher, was multiple blunt force trauma to the head, McCulloch said. No objects seem to have been used, he added.

Shelby Dasher told police she had been out part of the night and early morning before the incident. Her mother was at home all night but was not involved in the events leading up to Tyler's death, and no one else was involved, McCulloch said.

The medical examiner found no signs of past abuse, McCulloch said, adding that this was the exception to the rule in such cases.

Tyler and Shelby didn't sleep in the same room, McCulloch said.

Asked why he was charging Dasher with second-degree murder, not first-degree murder, McCulloch cited the lack of deliberation.

"It's the difference between hot-blooded and cold-blooded murder," he said.

McCulloch said the lesson for the community was, "Raising a child can be frustrating. There are a myriad of ways to deal with that. This isn't one of them."

After McCulloch spoke, St. Louis police chief Tim Fitch said the skills of his investigators and interrogators led Dasher to surrender information that led to the charge.

He said one of the first investigators on the scene recognized "rather quickly, thanks to his experience in cases of child abuse, this wasn't a missing or abducted child."

Tyler Dasher's body was found Tuesday near a cemetery about a mile from the Dasher home.

At approximately 11 a.m. Tuesday, police responded to a call reporting a missing child in southwestern St. Louis, police said. The child was last seen at 10 p.m. Monday, police said.

On Tuesday, Shelby Dasher told officers she overslept that morning, saw Tyler was missing and called the cops, according to the St. Louis Post-Dispatch.

At approximately 3:30 p.m. Tuesday, people walking their dog found a dead child in a wooded area about one mile from the Dasher home, police said. A county medical examiner confirmed it was Tyler, but did not determine cause of death, police said.

Police said they found no signs of a break-in at the Dasher home, where Shelby lived with her mother and son, the paper added.

Tyler's father, Joe Ellington, lives elsewhere. His parents are his co-guardians because Ellington was judged incapacitated or disabled, the Post-Dispatch said.